Hundreds of Shi'a have been killed by Iraqi security forces in the last six weeks according to Iraqi opposition sources quoted by the US State Department.

The State Department spokesman, James Rubin, says a brutal government campaign in mainly Shi'a southern Iraq was led by President Saddam Hussein's second son, Qusay, and resulted in mass arrests and the summary executions of hundred of prisoners.

Mr Rubin said the repression reached a peak in November. He said more than 2,000 civilians from villages in the southern marshes were taken hostage.

As well as the high state of tension with the US during that month, Baghdad said the Iraqi leader's deputy, Izzat Ibrahim, suffered an assassination attempt in the Shi'a holy city of Kerbala in the south.

After the attack took place Baghdad was reported to have sent extra troops to Kerbala and the propaganda campaign against opposition groups was stepped up. The opposition groups themselves started reporting mass killings at the time.

Assassination link

The State Department says the latest information comes from Shi'a dissidents and it believes it to be credible, but Baghdad customarily pours scorn on the credibility and importance of the exiled opposition.

The State Department links the arrests and executions to a spate of assassinations senior Shi'a clerics last year which the opposition says were carried out by the Iraqi authorities.

In the last three months the US and Britain have pursued a policy of increasing their support for Iraqi opposition groups in parallel to their bombardment of suspected Iraqi weapons sites.